DR. SCOFFERN ON THE MANUFACTURE OF SUGAR.* THE wonderful applications
of science to the profitable and comfortable arts, together with the desperate condition of the West Indian planters, have of late years directed a good deal of scientific attention to the cul- tivation and production of sugar. Most of the publications however, that have fallen in our way, have been exclusively addressed to the planter. All have referred to the properties and cultivation of the sugar- cane, many have been directed principally to these subjects, but all have been directed to the practices or the prejudices of the West Indian. The ablest of them, Dr. Evans's Sugar-Planter's Manual, rather aimed at introducing a better system of agriculture, and improving the existing processes of the West Indies, than applied itself to consider the manufac- ture of sugar as a chemical proceeding. This last is the distinguishing object of Dr. Scoffer°. In the work before us, he does not meddle with Tropical agriculture or plantation management. He admits the import- ance of crushing the sugar-cane so as to obtain all the juice it can be made to yield, but assigns the duty of obtaining it to the engineer. The difference between a chemical and a commercial process he does not dis- regard; but he holds that when a trite principle is once discovered, and the means of usefully applying it once established, the manufacturing is often more easy and economical than the chemical operation. With these views Dr. Scoffern has devoted himself for nearly two years to the experi- mental and practical manufacture of sugar; rather, however, to the re- fining of muscovado sugar than to the production of sugar from the "cane- juice," since not having been in the West Indies, he has been obliged to experimentahze on juice expressly imported for him. This fact, however, has no detrimental influence on his views, since the production of sugar from such "juice" must be more difficult than if treated when fresh from the cane.
Dr. Scoffern's main position is, that notwithstanding the variety of commercial terms for sugar, implying different qualities, and the various substances from which it may be extracted, a solution of sugar and water is essentially the same, whether made from beet-root or cane, muscovado or lump. The real difference arises from the impurities mixed with the so- lution; and to get rid of these in the completest and cheapest way, ought to be the object of the manufacturer whether in a West India boiling- house or a London refinery. The problem to be solved is thus stated- " Given a mixed solution of sugar, water, and impurities; how prac- tically to separate all but the sugar, with the least expense and the least delay." Some loss in effecting the removal of the impurities, small as is the proportion they bear to the whole quantity of sugar, is inevitable. The heat and the workings that are necessary to manufacture the juice into sugar have in themselves a destructive tendency: this loss is in- creased by bad management, and by the mischievous properties of the substance (lime) used as a purifier. A better cultivation, and the ex- pression of more cane-juice by a more powerful crushing in the mill, are important considerations ; but the main source of profit is to be sought
in an improved mode of manufacture.
"It will be the object of this treatise to set forth a process of sugar-manufac- ture which depends on the application of a chemical principle, and one involving no appliances save of the simplest kind. Indeed, the colonial sugar-producers have expected too much from machinery and too little from chemistry.
"The two operations of calico-printing and the production of soda from Bea salt furnish instances respectively of two well-marked kinds of chemical manu- facture—the qualitative and the quantitative. In the former, mere chemical agen- cies are brought into play without reference to any weighed chemical results. In the latter, the object, on the contrary, is to produce the practical maximum of some particular substance.
"In all manufactures of the latter class, it is evident that some amount of waste will take place. Nay, even in the laboratory, when engaged in analytic re- searches, when the appreciations of the minutest fraction of a grain is a desidera- tum, the chemist always suspects the truth of his own experiments if he do not encounter some trifling loss. "None, however, bat practical men, well conversant with laboratory and manu- facturing observations, can attain to a just estimate of the aerially small amount of this loss. The chemist will not expect to encounter more than one or two hundredths of a grain at most in a quantity of 1,000 grains: and if one per cent be set down as the average amount of loss encountered in a chemical manufacture, this statement will be assuredly an extreme one. In proportion, then, as any ði- cal manufacture should happen to present a greater loss than the above, so would it challenge our suspicion in regard to the correctness of the principles on which it depended. "If, then, after those preliminaries, the reader were to be told of the existence of a manufacture in which some 60 per cent of the material desired to be sepa- rated from only 1-7000th of impurities were destroyed in effecting that separa- tion, and that in being destroyed were converted into a foreign impurity, contami- nating the remaining 34 per cent ultimately obtained, his credulity would be largely drawn upon. " if, moreover, he were told that the aspirations and endeavours of the largest
bulk of individuals engaged in this manufacture lay in the direction, not of saving the 60 per cent lost—an endeavour considered by them as hopeless—but of * The manufacture of Sugar, in the Colonies and at Home, Chemically considered. ity John Scoifern, M.B. Loud., late Professor of Chemistry at the Aldeisfiate College Of Methane. Published by Longman and Co. producing economically a large excess of raw material, so that they might be able to afford this loss of 60 per cent, then the reader's incredulity would increase. Nevertheless, it is too true that such a manufacture does exist, and marked by the peculiarities indicated: it is the manufacture of sugar. "The juice of the sugar-cane, containing as it does merely 1-7000th of its weight of impurities, may be considered in relation to its specific gravity as a so- lution of sugar in pure water. Hence any of the available methods of taking the specific gravity of fluids may be employed as indicative of the amount of sugar in this material. That the test in question, i. e. of specific gravity, may be trusted as giving precise indications, has been demonstrated by frequently repeated che- mical experiments. "Both these methods of inquiry assure us that the amount of sugar in sugar- cane juice varies from about 17 to 23 per cent; whilst, according to the almost united testimony of all observers, 7 per cent of sugar (about one-third) is some- thing more than the average quantity obtained; and this too not in a condition of chemical parity, but admixed with numerous foreign matters."
The various processes of the manufacture under which this lose takes place—the chemical reasons, and sometimes the mere fact why, under the late systems, some part of it must have taken place, as well as a clear and complete account both of the manufacture of sugar in the West In- dies and of the refining it in Europe, will be found in the volume. Sul- phurous acid gas is the new precipitant, by which lime, and some other less practicable if less injurious bodies, are superseded as means of re- moving the impurities found in the solution. "The efficacy of this gas," says Dr. Scoffern, "has been tried on the large scale in a refinery, and also on cane-juice; in both cases with the most per- fect success." The successful application, however, is a matter for time and experiment to test, and on which we can offer no opinion. Our busi- ness is with the book as a treatise on the manufacture of sugar ; and as such it deserves high commendation. The distinction between the chemically and the commercially practicable is well kept in view ; while the superior advantages, when they exist, of the manufactory over the laboratory, are not overlooked. The principles of sugar-manufacture are clearly presented to the reader ; the methods used to carry them into ef- fect are succinctly and plainly described, without needless detail ; the latest methods of modern refineries are exhibited; and the whole is illus- trated by cuts which really are illustrations. In short, Dr. Scoffern's treatise is one of the best on the subject ; very useful if not indispensable to those engaged in the business, and interesting to those who only read for the purpose of acquiring information. It might have been improved by some account of the preliminary process of crushing, and a reiteration of the warning against the present wasteful system. As the real object of the author was to enforce the use of his discovery of the application of sulphurous acid gas to the purifying of sugar, a much fuller account of the methods and cost of employing it should have been given. Indeed, there is no account of them at all ; the reader is referred to another publication.
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